MY-PV Thor, Ohm-pilot or DIY water heating?

Q&A and troubleshooting DESS
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1

Good afternoon,

In 2016 we installed a self engineered system that works on the output frequency shift of a Victron inverter (3 Quattros) to heat the water.
We installed a Trumeter APM frequency meter, an Akytec TRM-210 PID process controller and 3 Fadisel R-27 5000W choppers connected to 3x2000W coils in one of the two 1000 litre “hot” tanks.
The PV field inverters we programmed to reduce power only above 51Hz, instead of the usual 50,20Hz.
The PID controller we programmed to keep the frequency in between 50,06 and 50,08Hz, so all the excess PV power will go in the hot water and the PV inverters keep producing the maximum possible.
This starts normally around 1300-1500 till sun down, as then our batteries are getting full and the Quattros want to reduce the PV power by raising the frequency, but instead water is heated.
We placed an extra APM frequency meter in the kitchen, so the “ladies” there would know when to switch on washing machines as these meters can be programmed to change colour, “red” not wash, “green” wash, even flashing if needed.
The results are in after 8 years of use, 1500 KWh in average each year, this with 8 KWp PV panels which generated 9000 KWh a year in average, meaning, at about 330 Euro savings a year if we had to buy that energy.

Just when we mounted this installation the Ohm-pilot was invented (2017-isch), but this one had/has only 1 proportional output and the other 2 are switched fully on/off.
The inverter phase connected to that proportional regulated coil is doing 80-90% of the work all year long, and not keeping the 3 phases in balance, for single phase no issues there.
Also it cannot be used without “again” a smart meter to see that nothing goes to the grid…

Then the MY-PV Thor was invented (2018-isch), mainly the 9S (3 phase) was of our interest, 3 phases fully proportional, frequency control and can be used with a smart meter, that’s cool we thought.

But, we lost quickly interest in both machines and even in our DIY made one…runs fine btw.
Why, easy, this amount of 1500 KWh for hot water was actually only a drip into the ocean, this as we also have 16KW vacuum tubes, generating 48000 KWh a year average and besides that, we use 2 pieces 75KW wood incinerators who deliver 40000 KWh a year average.
We thought that we “lost” way more energy due to the reduction of our panels, but it is not that much.
So, the safed energy with such device is not worth the investment, as it can take years of use to get it back in the pocket, also, it generates/saves only 1.5% on our hot water use per year in average.

Basically all 3 systems as above described are around a 1500-2500 Euro to build/install by yourself as it’s not just the controls part, but also the water coils, cabling, fuses, etc.
Well, with a return of 330 Euro per year on such investment in our case, that takes about 5-8 years before it starts to make a profit…maintenance and/or defects not calculated.
Over dimensioning the PV field was opted by us, but then again, more investment, and the risc that the frequency starts to limit the PV field inverters as well, and to have to set the clocks once a week correct…no…
For that investment it would be better to buy extra/bigger batteries or 1-2 extra vacuum tube panels is our conclusion as we do not deliver to the grid.

One big advantage of the TRM-210 is that it will keeps the frequency between 50,06 and 50,08Hz, unlike the PV inverters, which reduce only according a certain amount of power against frequency, having to set clocks all the time due to the high frequency, never late for work do…
Just for that I would advise to install such system.

Regards, Jeroen.

2

Is this a question or a ‘product presentation’? :thinking:

3

Good morning Steffen,

I like to see what other people think of these systems, therefore, I explained what we made, used, and what are the results after 8 years.
Hopefully others have these similar systems as well, so we can learn from each other and share usage experiences and results.
In 2016, when we designed the system we were actually first running on some obsolete analogue boards from a ships propulsion system we had laying around, perfectly proportional, but very outdated and very very expensive, so we opted for off the shelf products as written above.
It can be made with many other elements, it just what you prefer to use.
The above PID is now not made anymore, but many others are available, why we chose this TRM, it auto adjusts itself, very very handy, why the APM, completely adjustable, great screen, why the R-27s, standard electronics, easy to repair, as these are the “work horses”.
In the old community, I remember many people with “fast” running clocks, that problem we had also that time, but that we do not have anymore since we installed this system, as written above, thats a big win, for the costs not so much.

Regards, Jeroen.

4

:grinning: that should not be a criticism at all :slight_smile: That’s what this is supposed to be for

A few days ago there was just a ‘product presentation’ for a very inexpensive ‘modified’ 3-phase Shelly relay which could be integrated almost arbitrarily into the ‘’‘excess control’‘’ … so almost ready to use …

5

Good morning Steffen,

Yes of course, thanks for the “Shelly tip”, I’ve checked it.
That is not working on the frequency shift, nor with excess power from PV panels as I understood.
Nice to see btw.

Regards, Jeroen.

6

Good afternoon,

Seen the other posts of water heating lately with relays and the issues with such systems and the constant switching between soc%, etc, below is an about 300 euro fix for most installs.

A very easy solution to the switching issues (not to switch) is to use the APO M2 (newer model) from Trumeter and a Fadisel R27 (new PWM AC regulator model) when using PV inverter support assistant in VE-config.

Set PV inverter support assistant to 50.10-52.50Hz and complete off 53.00Hz.

Program the APO M2, 50.10-51.00Hz = 0-20mA and place a 500 Ohm resistor over that output to make it a 0-10V output.

Choose the positive curve on the Fadisel R27, 0-10V is 0-max power.

Program the PV inverter to reduce from 51.00-52.50Hz and complete off at 53.00Hz.

Now the system will consume all excess power from the panels and your batteries stay completely full at that time, not making switching from charging to discharging all the time due to switch operated controls, and so prolonging your battery life.

Especially Lithium, as reduced charging occurs from about 90% upwards and so the frequency already goes up around that point, and so already starting bringing power to your hot water proportional, not really of course as here is no PID controller as explained further up in this topic.

Both the APO M2 and the Fadisel use a 230V supply, so they can be hung right next to your hot water tank, and the R27 can handle easily a single coil up to 5000W, covering most single phase installs with excess power, and yes for 3 phase just buy 3 R27s and 1 APO, as the APO output can handle the mA to 3 R27s with ease.

How it works; the master Victron inverter starts to raise the frequency so slightly, say 50.00-50.10Hz, the APO is still hard zero out, the master goes above 50.10Hz, the APO starts to give a signal to the R27 and it starts to inject power to the hot water coil, the master still increases the frequency until it reaches exactly the surplus level of the PV inverter, and if the coil is fully activated at 51.00Hz and “if” there is still surplus, then the PV inverter starts to reduce, this as a safety as well.

Specially on clouded days this works very nice as a switched control cannot “see” that, but this system does that perfectly and the percentage of gained energy is way higher due to that, ok, one disadvantage of course, your frequency goes up as explained above in the original topic due to not having a PID controller in between, but normally it hangs way below 51.00Hz is this solution without PID controller.

So, now sizing of the coil, you know your install, example, say 5000Wp panels, constant use of power 1000W, inverters heat loss etc 300W, that means about 3700W surplus can occur, meaning a 3500W coil is good enough because also your panels will not deliver 5000W all day/year long.

Now sizing of the tank, for each 80-120L a 1000W coil can be used, meaning a coil of 3500W is good for 280-420L, this will normally heat your water by Delta 30-50 degrees Celsius average, seen the whole year average surplus, more in summer, less in winter, and mostly pending your PV panel angle.

Regards, Jeroen.